Dynamic biodiversity and ecosystem functioning in complex food webs

Background/Question/Methods Species diversity is under pressure at global and local scales, but the complexity of ecological communities hampers a general understanding of the consequences of animal species loss on ecosystem functioning. Two counteracting processes have been suggested to dominate the response of primary productivity to changing animal diversity: At high animal diversity, either enhanced direct feeding on plants may suppress primary productivity, or high rates of feeding within the animal community may indirectly release the plants from grazing pressure. We applied a dynamic food-web model, with body mass as a master trait determining metabolism and the strength of feeding interactions, to simulate the ecosystem functions of 15,000 communities across a diversity range between 10 and 100 animal species.

Results/Conclusions Surprisingly, we found that diverse animal communities indeed show higher feeding rates among animal species than less diverse communities, but nonetheless are more exploitative on plant biomass. Unravelling the plasticity of the community body-size structure reconciles the debate on the consequences of animal species loss from complex communities on a global scale.